U.S. patent application number 14/600467 was filed with the patent office on 2015-08-06 for blood sugar level measuring device and blood sugar level measuring method.
The applicant listed for this patent is SEIKO EPSON CORPORATION. Invention is credited to Hideto ISHIGURO, Hirokazu KASAHARA, Kimitake MIZOBE.
Application Number | 20150216482 14/600467 |
Document ID | / |
Family ID | 53725420 |
Filed Date | 2015-08-06 |
United States Patent
Application |
20150216482 |
Kind Code |
A1 |
KASAHARA; Hirokazu ; et
al. |
August 6, 2015 |
BLOOD SUGAR LEVEL MEASURING DEVICE AND BLOOD SUGAR LEVEL MEASURING
METHOD
Abstract
In a blood sugar level measuring device, a blood-sugar-level
predicting unit predicts a blood sugar level of a user. A light
emitting unit irradiates measurement light to the inside of a
living organism of the user. A light-emission control unit, a
measurement-point-candidate setting unit, a
light-amount-control-method determining unit, and a
measurement-point selecting unit control a light amount of
measurement light per one measurement on the basis of the predicted
blood sugar level. A light-reception control unit, a
light-absorption-spectrum generating unit, and a blood-sugar-value
calculating unit receive reflected light from the user and measure
a blood sugar level.
Inventors: |
KASAHARA; Hirokazu;
(Okaya-shi, JP) ; MIZOBE; Kimitake; (Pittsburgh,
PA) ; ISHIGURO; Hideto; (Shiojiri-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SEIKO EPSON CORPORATION |
Tokyo |
|
JP |
|
|
Family ID: |
53725420 |
Appl. No.: |
14/600467 |
Filed: |
January 20, 2015 |
Current U.S.
Class: |
600/301 ;
600/316 |
Current CPC
Class: |
A61B 5/4866 20130101;
A61B 5/681 20130101; A61B 5/1495 20130101; A61B 5/7275 20130101;
A61B 2560/0209 20130101; A61B 5/1118 20130101; A61B 5/14532
20130101; A61B 5/1455 20130101; G16H 40/63 20180101 |
International
Class: |
A61B 5/00 20060101
A61B005/00; A61B 5/1495 20060101 A61B005/1495; A61B 5/11 20060101
A61B005/11; A61B 5/145 20060101 A61B005/145; A61B 5/1455 20060101
A61B005/1455 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 31, 2014 |
JP |
2014-017025 |
Claims
1. A blood sugar level measuring device comprising: a predicting
unit configured to predict a blood sugar level of a user; a light
emitting unit for irradiating measurement light to an inside of a
living organism of the user; a light-amount control unit configured
to control a light amount of the measurement light per one
measurement on the basis of the predicted blood sugar level; and a
measuring unit configured to receive reflected light from the user
and measure a blood sugar level.
2. The blood sugar level measuring device according to claim 1,
wherein the predicting unit predicts a blood sugar level of the
user on the basis of a blood sugar level measured in past by the
measuring unit.
3. The blood sugar level measuring device according to claim 2,
wherein the predicting unit predicts a blood sugar level of the
user on the basis of a transition of the blood sugar level measured
in the past.
4. The blood sugar level measuring device according to claim 2,
wherein the predicting unit predicts, as a blood sugar level of the
user, a blood sugar level measured immediately before the
prediction.
5. The blood sugar level measuring device according to claim 1,
wherein the predicting unit adjusts the predicted blood sugar level
on the basis of at least any one of presence or absence of a meal
of the user and presence or absence of insulin administration.
6. The blood sugar level measuring device according to claim 5,
wherein the predicting unit adjusts the predicted blood sugar level
on the basis of dietary content of the user.
7. The blood sugar level measuring device according to claim 1,
further comprising a body-motion detecting unit for detecting a
body motion of the user, wherein the predicting unit adjusts the
predicted blood sugar level on the basis of a detection result of
the body-motion detecting unit.
8. The blood sugar level measuring device according to claim 1,
wherein the light-amount control unit controls, when the predicted
blood sugar level is in a first range, a light amount of the
measurement light using a first light amount control method and
controls, when the predicted blood sugar level is in a second range
higher than the first range, alight amount of the measurement light
using a second light amount control method with power consumption
smaller than power consumption in the first light amount control
method.
9. The blood sugar level measuring device according to claim 8,
further comprising an error calculating unit configured to
calculate a prediction error of the predicted blood sugar level on
the basis of a blood sugar level measured by the measuring unit
under the light amount control performed by the light-amount
control unit using the second light amount control method, wherein
when a predetermined condition indicating that the prediction error
is relatively large is satisfied, the measuring unit measures a
blood sugar level of the user again under the light amount control
performed by the light-amount control unit using the first light
amount control method.
10. The blood sugar level measuring device according to claim 8,
wherein the light amount control methods is defined by at least one
of the number of light emitting elements configuring the light
emitting unit, an amount of electric current supplied to the light
emitting unit, an exposure time of the light emitting unit, and
measurement wavelength width of the measurement light.
11. A blood sugar level measuring method comprising: predicting a
blood sugar level of a user; irradiating measurement light to an
inside of a living organism of the user; controlling a light amount
of the measurement light per one measurement on the basis of the
predicted blood sugar level; and receiving reflected light from the
user and measuring a blood sugar level.
Description
[0001] This application claims the benefit of Japanese Patent
Application No. 2014-017025, filed on Jan. 31, 2014. The content of
the aforementioned application is incorporated herein by reference
in its entirety.
BACKGROUND
[0002] 1. Technical Field
[0003] The present invention relates to a blood sugar level
measuring device and the like that measure a blood sugar level of a
user.
[0004] 2. Related Art
[0005] There is known a blood sugar level measuring device that
noninvasively measures glucose concentration, that is, a blood
sugar level in blood using light. Since the blood sugar level
greatly fluctuates even in a day because of meals, exercise, and
the like, the blood sugar level needs to be frequently measured.
Therefore, for diabetics and the like to measure and manage blood
sugar levels by themselves, there is a demand for a portable blood
sugar level measuring device for a continuous use. However, since
the blood sugar level measuring device is portable, the blood sugar
level measuring device relies on battery operation. A large
capacity battery is desirable from the viewpoint of, for example,
frequencies of charging and battery replacement. However, a small
capacity battery small in size and weight is desirable from the
viewpoint of portability. From all the viewpoints, an important
technique is a technique for reducing power consumption.
[0006] As the technique for reducing power consumption, for
example, a technique for intermittently performing measurement is
disclosed in JP-A-10-314150 (Patent Literature 1).
[0007] Incidentally, continuous measurement of a blood sugar level
is performed for the purpose of quick detection of a hypoglycemia
state in which a blood sugar level is low. Since the hypoglycemia
state is a fatal dangerous state, quick detection of the
hypoglycemia state is requested. When the technique for
intermittently performing measurement disclosed in Patent
Literature 1 is adopted, if a set measurement interval is too long,
there is a risk that detection of the hypoglycemia state is
delayed. The measurement interval is desirably short for the quick
detection of the hypoglycemia state. However, a reduction effect
for power consumption is not expected too much.
SUMMARY
[0008] An advantage of some aspects of the invention is to attain a
reduction in power consumption.
[0009] A first aspect of the invention is directed to a blood sugar
level measuring device including: a predicting unit configured to
predict a blood sugar level of a user; a light emitting unit for
irradiating measurement light to the inside of a living organism of
the user; a light-amount control unit configured to control a light
amount of the measurement light per one measurement on the basis of
the predicted blood sugar level; and a measuring unit configured to
receive reflected light from the user and measure a blood sugar
level.
[0010] As another aspect of the invention, the first aspect of the
invention may be configured as a blood sugar level measuring method
including: predicting a blood sugar level of a user; emitting
measurement light to the inside of a living organism of the user;
controlling a light amount of the measurement light per one
measurement on the basis of the predicted blood sugar level; and
receiving reflected light from the user and measuring a blood sugar
level.
[0011] If the light amount of the measurement light per one
measurement is reduced, power consumption can be suppressed.
According to the first and another aspects, it is possible to
predict a blood sugar level of the user and control the light
amount of the measurement light per one measurement on the basis of
the predicted blood sugar level. Therefore, it is possible to
attain a reduction in power consumption.
[0012] A second aspect of the invention is directed to the blood
sugar level measuring device according to the first aspect of the
invention, wherein the predicting unit predicts a blood sugar level
of the user on the basis of a blood sugar level measured in the
past by the measuring unit.
[0013] According to the second aspect of the invention, it is
possible to predict a blood sugar level of the user on the basis of
a blood sugar level measured in the past.
[0014] A third aspect of the invention is directed to the blood
sugar level measuring device according to the second aspect of the
invention, wherein the predicting unit predicts a blood sugar level
of the user on the basis of a transition of the blood sugar level
measured in the past.
[0015] A fourth aspect of the invention is directed to the blood
sugar level measuring device according to the second aspect of the
invention, wherein the predicting unit predicts, as a blood sugar
level of the user, a blood sugar level measured immediately before
the prediction.
[0016] According to the third aspect of the invention, it is
possible to predict a blood sugar level of the user on the basis of
a transition of the blood sugar level measured in the past.
According to the fourth aspect of the invention, it is possible to
predict, as a blood sugar level of the user, a blood sugar level
measured immediately before the prediction.
[0017] A fifth aspect of the invention is directed to the blood
sugar level measuring device according to any of the first to
fourth aspects of the invention, wherein the predicting unit
adjusts the predicted blood sugar level on the basis of at least
any one of presence or absence of a meal of the user and presence
or absence of insulin administration.
[0018] A blood sugar level during a meal shows a rising tendency
and a blood sugar level during insulin administration shows a
falling tendency. According to the fifth aspect of the invention,
it is possible to adjust the predicted blood sugar level on the
basis of at least any one of presence or absence of a meal of the
user and presence or absence of insulin administration. Therefore,
it is possible to improve prediction accuracy of a blood sugar
level.
[0019] A sixth aspect of the invention is directed to the blood
sugar level measuring device according to the fifth aspect of the
invention, wherein the predicting unit adjusts the predicted blood
sugar level on the basis of dietary content of the user.
[0020] As explained above, a blood sugar level during a meal shows
a rising tendency. However, a rising amount of the blood sugar
level fluctuates according to dietary content. According to the
sixth aspect of the invention, it is possible to adjust the
predicted blood sugar level on the basis of dietary content of the
user. Therefore, it is possible to further improve the prediction
accuracy of a blood sugar level.
[0021] A seventh aspect of the invention is directed to the blood
sugar level measuring device according to any of the first to sixth
aspects of the invention, wherein the blood sugar level measuring
device further includes a body-motion detecting unit for detecting
a body motion of the user, and the predicting unit adjusts the
predicted blood sugar level on the basis of a detection result of
the body-motion detecting unit.
[0022] A blood sugar level during exercise shows a falling
tendency. According to the seventh aspect of the invention, it is
possible to detect a body motion of the user and adjust the
predicted blood sugar level on the basis of a detection result.
Therefore, it is possible to improve the prediction accuracy of a
blood sugar level.
[0023] An eighth aspect of the invention is directed to the blood
sugar level measuring device according to any of the first to
seventh aspects of the invention, wherein the light-amount control
unit controls, when the predicted blood sugar level is in a first
range, a light amount of the measurement light using a first light
amount control method and control, when the predicted blood sugar
level is in second range higher than the first range, a light
amount of the measurement light using a second light amount control
method with power consumption smaller than power consumption in the
first light amount control method.
[0024] According to the eighth aspect of the invention, when the
predicted blood sugar level is in the first range, it is possible
to control a light amount of the measurement light per one
measurement using the first light amount control method. On the
other hand, when the predicted blood sugar level is in the second
range higher than the first range, it is possible to control a
light amount of the measurement light per one measurement using the
second light amount control method with power consumption smaller
than power consumption in the first light amount control
method.
[0025] A ninth aspect of the invention is directed to the blood
sugar level measuring device according to the eighth aspect of the
invention, wherein the blood sugar level measuring device further
includes an error calculating unit configured to calculate a
prediction error of the predicted blood sugar level on the basis of
a blood sugar level measured by the measuring unit under the light
amount control performed by the light-amount control unit using the
second light amount control method, and when a predetermined
condition indicating that the prediction error is relatively large
is satisfied, the measuring unit measures a blood sugar level of
the user again under the light amount control performed by the
light-amount control unit using the first light amount control
method.
[0026] According to the ninth aspect of the invention, if a
prediction error is large when the second light amount control
method with power consumption smaller than power consumption in the
first light amount control method is used, it is possible to
control a light amount of the measurement light per one measurement
using the first light amount control method and measure a blood
sugar level of the user again.
[0027] A tenth aspect of the invention is directed to the blood
sugar level measuring device according to the eighth or ninth
aspect of the invention, wherein the light amount control methods
is defined by at least one of the number of light emitting elements
configuring the light emitting unit, an amount of electric current
supplied to the light emitting unit, an exposure time of the light
emitting unit, and measurement wavelength width of the measurement
light.
[0028] According to the tenth aspect of the invention, it is
possible to define the light amount control methods with at least
one of the number of light emitting elements configuring the light
emitting unit, an amount of electric current supplied to the light
emitting unit, an exposure time of the light emitting unit, and
measurement wavelength width of the measurement light and control a
light amount of the measurement light per one measurement.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] The invention will be described with reference to the
accompanying drawings, wherein like numbers reference like
elements.
[0030] FIG. 1 is an external view showing an overall configuration
example of a blood sugar level measuring device in a first
embodiment.
[0031] FIGS. 2A and 2B are diagrams showing a configuration example
of a sensor module.
[0032] FIG. 3 is a diagram showing a Clarke Error Grid scatter
diagram.
[0033] FIG. 4 is a conceptual diagram showing an acquisition method
for a blood vessel position.
[0034] FIG. 5 is a diagram schematically showing a biological
image.
[0035] FIG. 6 is a diagram showing a blood vessel portion obtained
by excluding an accuracy deterioration factor region from a blood
vessel position shown in FIG. 5.
[0036] FIG. 7 is a diagram showing a blood vessel portion selected
on the basis of minimum region length.
[0037] FIG. 8 is a diagram for explaining propagation of light in a
biological tissue.
[0038] FIG. 9 is a diagram for explaining measurement point
candidate setting processing.
[0039] FIG. 10 is a block diagram showing a functional
configuration example of the blood sugar level measuring device in
the first embodiment.
[0040] FIG. 11 is a diagram showing a data configuration example of
a light amount control method list.
[0041] FIG. 12 is a diagram showing a data configuration example of
adjustment table for exercise time.
[0042] FIG. 13 is a diagram showing a data configuration example of
a measurement point candidate list.
[0043] FIG. 14 is a diagram showing a data configuration example of
a measurement result DB.
[0044] FIG. 15 is a flowchart for explaining a processing procedure
of first measurement processing.
[0045] FIG. 16 is a flowchart for explaining a detailed processing
procedure of blood sugar level prediction processing.
[0046] FIG. 17 is a flowchart for explaining a detailed processing
procedure of blood sugar level measurement processing.
[0047] FIG. 18 is a block diagram showing a functional
configuration example of a blood sugar level measuring device in a
second embodiment.
[0048] FIG. 19 is a flowchart for explaining a processing procedure
of second measurement processing.
DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0049] Modes for carrying out a blood sugar level measuring device
and a blood sugar level measuring method according to the invention
are explained below with reference to the drawings. Note that the
invention is not limited by embodiments explained below. Modes to
which the invention is applicable are not limited to the
embodiments. In the description of the drawings, same portions are
denoted by the same reference numerals and signs.
First Embodiment
Overall Configuration
[0050] FIG. 1 is an external view showing an overall configuration
example of a blood sugar level measuring device 10 of a noninvasive
type in a first embodiment. The blood sugar level measuring device
10 functions as a measuring instrument that measures blood glucose
concentration (so-called "blood sugar level") of a user 2 and also
functions as a data logger that stores measurement data. The blood
sugar level measuring device 10 can be considered a kind of a
computer. As shown in FIG. 1, the blood sugar level measuring
device 10 is configured as, for example, a wearable device of a
wristwatch type. The blood sugar level measuring device 10 is used
by being mounted and fixed to a body part such as the arm, the leg,
or the neck of the user 2 by a band 14 provided in a main body case
12.
[0051] The blood sugar level measuring device 10 includes, on the
front surface of the main body case 12 (a surface facing outward
when the blood sugar level measuring device 10 is mounted on the
user 2), as operation input means, an operation switch 16 and a
touch panel 18 also functioning as image display means. The user 2
can perform various kinds of operation inputs such as measurement
start operation using the operation switch 16 and the touch panel
18.
[0052] The blood sugar level measuring device 10 includes, on a
side surface of the main body case 12, a communication device 20 to
and from which a wired cable for communicating with an external
apparatus can be attached and detached and a reader writer 24 that
realizes reading and writing of data from and to a memory card 22.
The blood sugar level measuring device 10 includes, on the rear
surface (a surface in contact with the skin of the user 2 when the
blood sugar level measuring device 10 is mounted on the user 2)
side of the main body case 12, a sensor module 50 functioning as a
main sensor for irradiating measurement light to the inside of a
living organism of the user 2 as an irradiation wave and receiving
reflected light and an acceleration sensor 27. A built-in battery
26 of a charging type and a control substrate 30 are incorporated
in the inside of the main body case 12.
[0053] If the communication device 20 is configured to perform the
communication with the external apparatus by radio, the
communication device 20 is realized by a radio communication module
and an antenna.
[0054] The memory card 22 is a nonvolatile memory of a detachable
type capable of rewriting data. As the memory card 22, besides a
flash memory, rewriteable nonvolatile memories such as a
ferroelectric memory (FeRAM: Ferroelectric Random Access Memory)
and a magnetic resistance memory (MRAM: Magnetoresistive Random
Access Memory) can be used.
[0055] A charging system to the built-in battery 26 can be set as
appropriate. For example, a configuration may be adopted in which
an electric contact is separately provided on the rear surface side
of the main body case 12 and the built-in battery 26 is set in a
cradle connected to a domestic power supply and is energized and
charged through the cradle via the electric contact. Wireless
charging of a noncontact type may be adopted.
[0056] The acceleration sensor 27 detects an acceleration vector of
the user 2. For example, the blood sugar level measuring device 10
determines an exercise state of the user 2 using, as detected
acceleration, detection axis components of an X axis, a Y axis, and
a Z axis of the acceleration sensor 27 inscribed in the vicinity of
the main body case 12 in FIG. 1.
[0057] The control substrate 30 collectively controls the blood
sugar level measuring device 10. Specifically, the control
substrate 30 is mounted with a CPU (Central Processing Unit) 32, a
main memory 34, a memory for measurement data 36, a touch panel
controller IC (Integrated Circuit) 38, and a sensor module
controller 40. Besides, electronic components such as a power
supply management IC and an IC for image processing can be mounted
as appropriate.
[0058] The main memory 34 is a storage medium that can store a
computer program and initial setting data and store an arithmetic
value of the CPU 32. The main memory 34 is realized using a RAM, a
ROM, a flash memory, and the like as appropriate. Note that the
computer program and the initial setting data may be stored in the
memory card 22.
[0059] The memory for measurement data 36 is a data-rewritable
nonvolatile memory and is a storage medium for storing measurement
data of a blood sugar level. As the memory for measurement data 36,
besides a flash memory, rewritable nonvolatile memories such as a
ferroelectric memory (FeRAM) and a magnetic resistance memory
(MRAM) can be used. Note that the measurement data may be stored in
the memory card 22.
[0060] The touch panel controller IC 38 is an IC that realizes a
driver function for causing the touch panel 18 to display an image
and a function for realizing a touch input. The touch panel
controller IC 38 and the touch panel 18 can be realized by using a
publicly-known technique as appropriate.
[0061] The sensor module controller 40 includes an IC or a circuit
that performs an irradiating function for measurement light by the
sensor module 50 and a light receiving function for measurement
light transmitted through a biological tissue of the user 2
(transmitted light) and the measurement light reflected on the
biological tissue (reflected light).
[0062] More specifically, the sensor module controller 40 includes
a light emitting controller unit 42 including an IC or a circuit
that individually controls a plurality of light emitting elements
(elements that emit measurement light through energization)
included in the sensor module 50 and a light receiving controller
unit 44 including an IC or a circuit that controls light reception
by a plurality of light receiving elements (elements that emit
electric signals corresponding to a received light amount) included
in the sensor module 50.
[0063] Note that the sensor module controller 40 may be configured
by a plurality of ICs. For example, the IC or the circuit
equivalent to the light emission controller unit 42 and the IC or
the circuit equivalent to the light reception controller unit 44
can also be configured as separate ICs. Alternatively, a part of
these functions may be realized by the CPU 32.
[0064] FIGS. 2A and 2B are diagrams showing a configuration example
of the sensor module 50. FIG. 2A is a front view and FIG. 2B is a
sectional view. Note that, to facilitate understanding, light
emitting elements 52 and light receiving elements 54 are
intentionally shown large. The size, the aspect ratio, and the like
of the sensor module 50 are not limited to those shown in the
figures and can be set as appropriate.
[0065] The sensor module 50 is a device configured by stacking a
layer in which a plurality of the light emitting elements 52 are
arrayed in a plane shape and a layer in which a plurality of the
light receiving elements 54 are arrayed in a plane shape. In other
words, the sensor module 50 is an image sensor of a light source
built-in type and is a sensor array that realizes both functions of
irradiation and reception of measurement light. The sensor module
50 may be configured integrally with the sensor module controller
40.
[0066] The light emitting elements 52 are light emitting units that
irradiate the measurement light and can be realized by, for
example, an LED (Light Emitting Diode) or an OLED (Organic
light-emitting diode). When a blood sugar level is measured, the
light emitting elements 52 are elements capable of emitting light
including near infrared light close to a visible region having
subcutaneous transmittivity.
[0067] The light receiving elements 54 are image pickup elements
that receive the transmitted light and the reflected light of the
measurement light and output an electric signal corresponding to a
light reception amount. The light receiving elements 54 can be
realized by a semiconductor element such as a CCD (Charge Coupled
Device Image Sensor) or a CMOS (Complementary Metal Oxide
Semiconductor Image Sensor). One light receiving element 54
includes a plurality of elements that receive RGB wavelength
components.
[0068] The sensor module 50 includes 1) a light receiving layer 51
in which the plurality of light receiving elements 54 are arrayed
in a plane shape and a lattice shape, 2) a light blocking layer 53
that selectively blocks lights other than lights traveling to the
light receiving elements 54, 3) a spectral layer 55 that
selectively transmits near infrared light, and 4) a light emitting
layer 57 in which the plurality of light emitting elements 52 are
arrayed in a plane shape and a lattice shape between light
receiving elements adjacent to each other in positions where the
light emitting elements 52 do not hinder an optical path of the
lights transmitted through and reflected on the biological tissue
and reaching the light receiving elements 54. The light receiving
layer 51, the light blocking layer 53, the spectral layer 55, and
the light emitting layer 57 are stacked in order from a base side
(the front side of the main body case 12).
[0069] Like a publicly-known CCD image sensor, the light receiving
elements 54 of the light receiving layer 51 are arranged in a
matrix shape in which pixels can be identified in an Xs-Ys
rectangular coordinate system. That is, the sensor module 50
functions in the same manner as the publicly-known image sensor.
Note that the shape, the size, and the arrangement pattern of the
light receiving elements 54 can be set as appropriate.
[0070] The light emitting elements 52 of the light emitting layer
57 are arranged one by one in a butting portion of corners of the
light receiving elements 54 in the vicinity when the sensor module
50 is viewed from the front (the rear side of the main body case
12). More specifically, one light emitting element 52 is arranged
in a butting portion of corners of four light receiving elements
54. All the light emitting elements 52 are arranged in a matrix
shape in which the light emitting elements 52 can be identified in
an Xs-Ys rectangular coordinate system same as that of the light
receiving elements 54. The sensor module 50 includes a driving
mechanism that causes the light emitting elements 52 to selectively
emit light. For example, the light emitting elements 52 can be
drive-controlled in the same manner as an active matrix system of a
liquid crystal panel display.
[0071] For manufacturing of the sensor module 50 having such a
stacked structure, a semiconductor microfabrication technique used
for manufacturing of the publicly-known CCD image sensor and an
OLED display can be applied as appropriate.
[0072] Note that the size and the arrangement interval of the light
emitting elements 52, the size and the arrangement interval of the
light receiving elements 54, and the like can be set as
appropriate. For example, the arrangement intervals are suitably
set to 1 to 500 [.mu.m] and can be set to, for example, about 50 to
200 [.mu.m] according to a balance between manufacturing costs and
measurement accuracy. In the sensor module 50, a condensing layer
including a further optical element can be provided for the purpose
of narrowing an irradiation range of the measurement light
irradiated by the light emission of the light emitting elements 52
and deflecting the measurement light or accurately collecting, in
the light receiving elements 54, the lights transmitted through and
reflected on the biological tissue. A protection layer or the like
that prevents damage to the surface of the sensor module 50 may be
provided as appropriate. The sensor module 50 is not limited to the
configuration in which the light emitting elements 52 and the light
receiving elements 54 are stacked. The light emitting elements 52
and the light receiving elements 54 may be placed side by side.
Overview
[0073] In the first embodiment, a blood sugar level of the user 2
is predicted (the predicted blood sugar level is hereinafter
referred to as "predicted blood sugar level") on the basis of a
measurement value of a blood sugar level measured in the past
(hereinafter referred to "measured blood sugar level" as
appropriate). A light amount per one measurement, more
specifically, an overall amount of light amounts of the light
emitting elements 52 caused to emit lights in one measurement is
controlled on the basis of the predicted blood sugar level to
measure a blood sugar level. The control of the light amount is
performed by selectively applying a different plurality of light
amount control methods.
[0074] If the light amount per one measurement is not limited, a
blood sugar level can be measured at highest accuracy. On the other
hand, if the light amount per one measurement is reduced, although
the measurement accuracy is deteriorated because of a factor such
as a decrease in an S/N ratio, power consumption can be
suppressed.
[0075] As a method of evaluating an allowable error of a
measurement value with respect to a true value of a blood sugar
level, a method called Clarke Error Grid analysis is known. FIG. 3
is a diagram showing a Clarke Error Grid scatter diagram. In
general, in a hypoglycemia state, high measurement accuracy is
requested and an allowable error of a measurement value is small.
In other words, when a blood sugar level is high, requested
measurement accuracy is relaxed compared with when a blood sugar
level is low. For example, in the Clarke Error Grid analysis, if a
relation between a true value and a measurement value belongs to an
A zone in the scatter diagram shown in FIG. 3, it is considered
that there is clinically sufficient measurement accuracy. However,
an error range of the A zone narrows as the true value decreases.
As a specific numerical value, if an error rate of the measurement
value with respect to the true value is generally within .+-.20%,
it is considered that the relation belongs to the A zone.
[0076] Therefore, in the first embodiment, two kinds of light
amount control methods, i.e., a first light amount control method
and a second light amount control method are defined beforehand
according to the number of the light emitting elements 52 caused to
emit lights in measurement (the number of light emitting positions
(light emitting elements for measurement 52-1) explained below;
hereinafter referred to as "number of light emitting elements").
Specifically, the number of light emitting elements of the second
light amount control method is defined as a number smaller than the
number of light emitting elements of the first light amount control
method. However, in both the light amount control methods, the
number of light emitting elements is defined on the basis of a
number with which required measurement accuracy can be
realized.
[0077] When the predicted blood sugar level is low, the first light
amount control method is applied to realize high measurement
accuracy. On the other hand, when the predicted blood sugar level
is high, the second light amount control method with small power
consumption is applied to reduce power consumption while securing
requested measurement accuracy.
[0078] Prior to measurement, the blood sugar level measuring device
10 is fixed by the band 14 to cause the rear surface, on which the
sensor module 50 is exposed, to adhere to the skin of the user 2.
By causing the sensor module 50 to adhere to the skin, it is
possible to suppress factors of deterioration in measurement
accuracy such as reflection of the measurement light on the skin
surface and scattering of the measurement light in a tissue near
the skin surface.
[0079] As a measurement procedure for a blood sugar level, first, a
blood vessel present under the skin of a body covered with the
sensor module 50 is selected. Irradiation and reception of the
measurement light are performed targeting the selected blood
vessel. Thereafter, a blood vessel transmitted light component
transmitted through the blood vessel is extracted from a light
reception result (intensity of received light). A blood sugar level
is calculated from a relative spectrum (a light absorption
spectrum) that reflects an amount of the blood vessel transmitted
light component.
[0080] To select a blood vessel, it is necessary to grasp where
under the skin covered with the sensor module 50 the blood vessel
is present. FIG. 4 is a conceptual diagram showing an acquisition
method for a blood vessel position and is equivalent to a sectional
view of a portion of the user 2 covered with the sensor module 50.
Note that the sensor module 50 is shown in a simplified form.
[0081] In acquisition of a blood vessel position, first, in the
same manner as vein pattern detection in a publicly-known vein
authentication technique, the light emitting elements 52 included
in the sensor module 50 are caused to emit lights all at once to
irradiate the measurement light to an entire mounted part of the
sensor module 50. Lights transmitted through and reflected on a
biological tissue under the skin (a subcutaneous tissue) are
received (photographed) by using all the right receiving elements
54 to acquire a biological image.
[0082] The biological image acquired by the sensor module is a set
of luminance data of pixels respectively corresponding to the light
receiving elements 54 of the sensor module 50 and is obtained as a
two-dimensional image of an Xs-Ys rectangular coordinate system
same as a pixel coordinate of the sensor module 50. Because of the
influence of blood flowing on the inside of the blood vessel, the
blood vessel absorbs near infrared light more than a place where a
blood vessel 7 is absent. Therefore, the blood vessel position has
lower luminance than a region other than the blood vessel position.
Therefore, by extracting a region where luminance is low in the
biological image, it is possible to identify, for each of the
pixels, whether the blood vessel is in a photograph, in other
words, whether the blood vessel is present under the light
receiving elements 54. "Under the light receiving elements 54" is
an expression suitable for operation explanation of the device for
the user 2. More accurately, "under the light receiving elements
54" means an opposed direction of the light receiving elements 54
across the skin surface (a direction in which light is
received).
[0083] FIG. 5 is a diagram schematically showing the biological
image. In an example shown in FIG. 5, a belt-like region hatched by
oblique lines or dot patterns indicates the position of the vessel
7. White void parts indicate biological tissue portions (non-blood
vessel sections) 8 where the blood vessel 7 is absent under the
skin. Note that the acquisition method for a blood vessel position
is not limited to the illustrated method. For example, it is also
conceivable adopt a method of acquiring a relative position of a
biological inner structure beforehand using a publicly-known
biological tomographic image measuring technique such as ultrasonic
echo or MRI (Magnetic Resonance Imaging), or CT (Computed
Tomography) and determining a blood vessel position on the basis of
the relative position.
[0084] If the position of the vessel 7 is acquired, a blood vessel
portion suitable for measurement is selected as a measurement
target region. First, blood vessel portions such as branching
points and merging points of the blood vessel 7 indicated by broken
line circles and biological image end portions indicated by
alternate long and short dash line circles in FIG. 5 are excluded
as portions that could be factors of deterioration in measurement
accuracy (accuracy deterioration factor portions). This is because,
if the measurement light reaches the branching points and the
merging points of the blood vessel, it is likely that transmitted
light and reflected light of the non-blood vessel sections 8 other
than the blood vessel are mixed in received light in a light
receiving position and the mixed light affects a light absorption
spectrum of blood vessel transmitted light, which is originally
desired to be obtained, and deteriorates the measurement accuracy.
Blood vessel portions of the biological image end portions
indicated by the alternate long and short dash line circles are
excluded because it is likely that branching points and merging
points of the blood vessel are present in the vicinity of the outer
side of a photographing range. FIG. 6 a diagram showing an example
of blood vessel portions 7a obtained by excluding the accuracy
deterioration factor portions from the blood vessel position shown
in FIG. 5. For example, hatched portions of oblique lines are the
blood vessel portions 7a remaining without being excluded.
[0085] Irradiated lights from the light emitting elements 52 are
diffused and reflected in the biological tissue. A part of the
irradiated lights is received by the light receiving elements 54.
That is, a part of the lights received by the light receiving
elements 54 changes to blood vessel transmitted light. As a ratio
of the blood vessel transmitted light is higher, it is possible to
obtain a light absorption spectrum more conspicuously representing
characteristics of components in the blood. Therefore, the
measurement accuracy is higher. A relatively thin blood vessel is
extracted thin in a blood vessel pattern specified from the
biological image. In some case, for example, the thin blood vessel
is discontinuously extracted. A blood vessel present in a
relatively deep position is also discontinuously extracted because
a light amount of the blood vessel transmitted light is small.
Therefore, a blood vessel portion having length equal to or larger
than predetermined minimum region length is selected and set as a
measurement target region. The length of the blood vessel portion
may be set to, for example, the length of a center line L of the
blood vessel portion or may be set to the number of pixels
configuring the center line L. FIG. 7 is a diagram showing an
example of finally selected blood vessel portions 7b. For example,
the blood vessel portions 7b indicated by hatching of oblique lines
are selected on the basis of "minimum region length".
[0086] If the blood vessel portions 7b suitable for measurement are
selected as measurement target regions, a light emitting position
(a light emitting element for measurement) of the measurement
light, a light receiving position (a light receiving element for
measurement) appropriate for obtaining blood vessel transmitted
light (transmitted light of the blood vessel portions 7b), and a
light receiving position (a light receiving element for reference)
appropriate for obtaining transmitted light for reference are
selected. The transmitted light for reference means light not
transmitted through the blood vessel portions 7b and transmitted
through only the non-blood vessel sections 8 in the vicinity of the
blood vessel portions 7b.
[0087] FIG. 8 is a diagram for explaining propagation of light in
the biological tissue. A sectional view taken along the depth
direction is shown. Measurement light irradiated from a certain
light emitting element 52 is diffused and reflected in the
biological tissue. A part of the irradiated measurement light
reaches the light receiving element 54. A propagation route of the
light is formed in a so-called banana shape (a region between two
arcs). Width in the depth direction is the largest substantially
near the center. The depth (reachable depth) of the propagation
route is smaller as the interval between the light emitting element
52 and the light receiving element 54 is smaller. The depth is
larger as the interval is larger.
[0088] To improve the measurement accuracy, it is desirable that
more blood vessel transmitted light is received by the light
receiving element 54. Therefore, an optimum interval (an optimum
distance) W between the light emitting element 52 and the light
receiving element 54 can be set according to assumed depth (the
distance from the skin surface to the blood vessel center) D of the
blood vessel 7 on the premise that the blood vessel 7 is located
substantially in the center between the light emitting element 52
and the light receiving element 54. The optimum distance W is a
distance about two times as large as the depth D of the blood
vessel 7. For example, when the depth D is about 3 mm, the optimum
distance W is about 5 to 6 mm.
[0089] Therefore, a first relative position condition is set as
"the blood vessel 7 is located in the center portion between the
light emitting position and the light receiving position for
measurement and the distance between the light emitting position
and the light receiving position for measurement is equal to the
predetermined optimum distance W". The light emitting element 52
and the light receiving element satisfying the first relative
position condition are searched and selected as the light emitting
position and the light receiving position for measurement. In
addition, a second relative position condition is set as "the blood
vessel 7 is absent between the light emitting position and the
light receiving position for reference and the distance between the
light emitting position and the light receiving position for
reference is equal to the predetermined optimum distance W". The
light receiving element 54 satisfying the second relative position
condition is selected as the light receiving position for
reference.
[0090] Actually, the light emitting position, the light receiving
position for measurement, and the light receiving position for
reference are selected for each of a plurality of measurement point
candidates (measurement point candidate setting processing). FIG. 9
is a diagram for explaining the measurement point candidate setting
processing. In the measurement point candidate setting processing,
for example, as indicated by "x" marks in FIG. 9, measurement point
candidates are set at a predetermined interval on the center lines
L of the blood vessel portions 7b. A combination of the light
emitting element 52 and the light receiving element 54 satisfying
the first relative position condition and satisfying the second
relative position condition is searched for each of the measurement
point candidates. For example, if attention is paid to one
measurement point candidate P11, the light emitting element 52 and
the light receiving element 54, in the center portion between which
the measurement point candidate P11 is located and the distance
between which is the optimum distance W, are respectively set as a
light emitting element for measurement 52-1 and a light receiving
element for measurement 54-1 to select the light emitting position
and the light receiving position for measurement. The light
receiving position for reference is selected on an extended line
connecting the light emitting position and the light receiving
position for measurement and on the opposite side of the light
receiving position for measurement when viewed from the light
emitting position. The light receiving position for reference is
set as a light receiving element for reference 54-2. It is assumed
that all of the light emitting position, the light receiving
position for measurement, and the light receiving position for
reference are not located on the blood vessel 7 (are located on the
non-blood vessel sections 8). Concerning the other measurement
point candidates, the light emitting position, the light receiving
position for measurement, and the light receiving position for
reference are selected in the same manner. Note that, if the
combination of the light emitting element 52 and the light
receiving element 54 satisfying the first relative position
condition and satisfying the second relative position condition is
absent, the measurement point candidate corresponding to the light
emitting position, the light receiving position for measurement,
and the light receiving position for reference is deleted.
[0091] If the light emitting position, the light receiving position
for measurement, and the light receiving position for reference are
selected for each of the plurality of measurement point candidates
as explained above, a blood sugar level of the user 2 is predicted.
The first light amount control method or the second light amount
control method is selectively applied on the basis of the predicted
blood sugar level to determine the number of light emitting
elements and select measurement point candidates equivalent to the
determined number of light emitting elements as measurement
points.
[0092] Subsequently, the light emitting positions (the light
emitting elements for measurement 52-1) at all the measurement
points are caused to emit lights to irradiate the measurement
light. The blood vessel transmitted light component is extracted
for each of the measurement points from light reception results in
the light receiving positions for measurement (the light receiving
elements for measurement 54-1) and the light receiving positions
for reference (the light receiving elements for reference 54-2)
corresponding to the light emitting positions. For example, a
wavelength .lamda. of the measurement light is changed in a near
infrared region by causing each of the light emitting elements for
measurements 52-1 to emit light while shifting light emission
wavelength thereof by predetermined measurement wavelength at a
time. Transmittance T(.lamda.) of the blood vessel transmitted
light is calculated for each wavelength .lamda. concerning each of
the measurement points. Note that a configuration in which the
wavelength .lamda. of the measurement light is changed is not
limited to the configuration in which the light emission wavelength
of the light emitting element for measurement 52-1 is shifted by
predetermined measurement wavelength width at a time. The
wavelength .lamda. of the measurement light may be changed by
changing transmission band width of a spectral filter for each
predetermined measurement wavelength width.
[0093] The transmittance T(.lamda.) at the measurement points can
be calculated from light intensity Os(.lamda.) obtained by the
light receiving element 54 for measurement and light intensity
Or(.lamda.) obtained by the light receiving element 54 for
reference according to the following Expression (1). Light
absorptivity is calculated from the calculated transmittance
T(.lamda.) and a light absorption vector is generated.
T(.lamda.)=Os(.lamda.)/Or(.lamda.) (1)
[0094] Thereafter, a blood sugar level is calculated (estimated)
from the light absorption spectrum using a "calibration curve"
indicating a relation between blood glucose concentration and light
absorbance set in advance. Note that concerning a method of
generating a light absorption spectrum and calculating a blood
sugar level, a publicly-known technique can be adopted as
appropriate.
Functional Configuration
[0095] FIG. 10 is a block diagram showing a main functional
configuration example of the blood sugar level measuring device 10
in the first embodiment. As shown in FIG. 10, the blood sugar level
measuring device 10 includes a sensor unit 110, a body-motion
detecting unit 120, an operation input unit 130, a display unit
140, a communication unit 150, a processing unit 160, and a storing
unit 180.
[0096] The sensor unit 110 corresponds to the sensor module 50
shown in FIGS. 2A and 2B. The sensor unit 110 includes a light
emitting unit 111 configured by the plurality of light emitting
elements 52 and a light receiving unit 113 configured by the
plurality of light receiving elements 54. Arrangement positions
(Xs-Ys coordinate values) of the light emitting elements 52
configuring the light emitting unit 111 are stored in the storing
unit 180 in advance as a light emitting element list 183 in which
the arrangement positions are associated with light emitting
element numbers allocated to the relevant light emitting elements
52. Arrangement positions (Xs-Ys coordinate values) of the light
receiving elements 54 configuring the light receiving unit 113 are
stored in the storing unit 180 in advance as a light receiving
element list 184 in which the arrangement positions are associated
with light receiving element numbers allocated to the relevant
light receiving elements 54.
[0097] The body-motion detecting unit 120 is a unit for detecting a
body motion. For example, the body-motion detecting unit 120 can be
realized using a MEMS (Micro Electro Mechanical Systems) sensor.
The acceleration sensor 27 shown in FIG. 1 corresponds to the
body-motion detecting unit 120. The body-motion detecting unit 120
outputs detected acceleration to the processing unit 160 at any
time.
[0098] The operation input unit 130 is realized by various switches
such as a button switch and a dial switch and an input device such
as a touch panel. The operation input unit 130 outputs an operation
input signal to the processing unit 160 according to various
operation inputs performed by the user 2. The operation switch 16
and the touch panel 18 shown in FIG. 1 correspond to the operation
input unit 130.
[0099] The display unit 140 is realized by a display device such as
an LCD (Liquid Crystal Display) or an EL display
(Electraluminescence display). The display unit 140 displays
various screens on the basis of a display signal input from the
processing unit 160. The touch panel 18 shown in FIG. 1 corresponds
to the display unit 140.
[0100] The communication unit 150 is a communication device for
transmitting and receiving information used inside the device
between the communication unit 150 and an external information
processing apparatus under the control by the processing unit 160.
The communication device 20 shown in FIG. 1 corresponds to the
communication unit 150. As a communication system of the
communication unit 150, it is possible to adopt various systems
such as a form of connecting the communication unit 150 by wire via
a cable conforming to a predetermined communication standard, a
form of connecting the communication unit 150 to a charger called
cradle via an intermediate device, and a form of connecting the
communication unit 150 by radio using radio communication.
[0101] The processing unit 160 is realized by a microprocessor such
as a CPU (Central Processing Unit) or a DSP (Digital Signal
Processor) and a control device and an arithmetic device such as an
ASIC (Application Specific Integrated Circuit). The processing unit
160 collectively controls the units of the blood sugar level
measuring device 10. The control substrate 30 shown in FIG. 1
corresponds to the processing unit 160. The processing unit 160
includes a light-emission control unit 161, a light-reception
control unit 162, a blood-vessel-position acquiring unit 163, a
measurement-point-candidate setting unit 164, an exercise-state
determining unit 165, a blood-sugar-level predicting unit 166
functioning as a predicting unit, a light-amount-control-method
determining unit 168, a measurement-point selecting unit 169, a
light-absorption-spectrum generating unit 170, and a
blood-sugar-level calculating unit 171. Note that the units
configuring the processing unit 160 may be configured by hardware
such as a dedicated module circuit.
[0102] The light-emission control unit 161 individually controls
light emission of the light emitting elements 52 configuring the
light emitting unit 111. For example, the light-emission control
unit 161 can be realized by using a driving control technique of a
so-called active matrix system. The light-emission control unit 161
functions as alight-amount control unit together with the
measurement-point-candidate setting unit 164, the
light-amount-control-method determining unit 168, and the
measurement-point selecting unit 169.
[0103] The light-reception control unit 162 performs control for
reading out, from received light received by the light receiving
elements 54 of the light receiving unit 113, an electric signal
corresponding to the intensity of the received light. The
light-reception control unit 162 functions as a measuring unit
together with the light-absorption-spectrum generating unit 170 and
the blood-sugar-level calculating unit 171.
[0104] The blood-vessel-position acquiring unit 163 acquires a
biological image under the skin covered with the sensor module 50
(see FIG. 5), processes the biological image to acquire a blood
vessel position, and selects a blood vessel portion suitable for
measurement as a measurement target region. The acquisition of the
blood vessel position is realized by using, as appropriate, a
photographing technique for a biological image in a publicly-known
vein authentication technique or the like or a technique for
identifying a vein pattern from a biological image in the
publicly-known vein authentication technique or the like.
[0105] The measurement-point-candidate setting unit 164 is a
functional unit that performs measurement point candidate setting
processing. The measurement-point-candidate setting unit 164 sets a
plurality of measurement point candidates along the blood vessel
portion set as the measurement target region. In this case, the
measurement-point-candidate setting unit 164 searches for a
combination of the light emitting element 52 and the light
receiving element 54 satisfying the first relative position
condition and satisfying the second relative position condition to
select, for each of the measurement point candidates, the light
emitting position (the light emitting element for measurement
52-1), the light receiving position for measurement (the light
receiving element for measurement 54-1), and the light receiving
position for referenced (the light receiving element for reference
54-2) in advance. The optimum distance W is stored in the storing
unit 180 in advance as optimum distance data 185.
[0106] The exercise-state determining unit 165 calculates exercise
intensity on the basis of the detected acceleration input from the
body-motion detecting unit 120 and determines an exercise state of
the user 2 (whether the user 2 is performing exercise).
[0107] The blood-sugar-level predicting unit 166 predicts a blood
sugar level of the user 2 on the basis of a measured blood sugar
level in the past. The blood-sugar-level predicting unit 166
includes an adjusting unit 167 that adjusts the predicted blood
sugar level on the basis of the exercise intensity of the user 2
and meal information and insulin administration information
acquired by receiving an operation input of the user 2.
[0108] The light-amount-control-method determining unit 168
selectively applies the first light amount control method or the
second light amount control method on the basis of the predicted
blood sugar level and determines the number of light emitting
elements.
[0109] The measurement-point selecting unit 169 selects, as
measurement points, measurement point candidates equivalent to the
number of light emitting elements out of the measurement point
candidates.
[0110] The light-absorption-spectrum generating unit 170 causes the
light emitting elements for measurement 52-1 at all the measurement
points to irradiate measurement light under the control by the
light-emission control unit 161 and the light-reception control
unit 162. The light-absorption-spectrum generating unit 170
generates a light absorption spectrum on the basis of light
reception results of the light receiving elements for measurement
54-1 and the light receiving elements for reference 54-2 at all the
measurement points.
[0111] The blood-sugar-level calculating unit 171 calculates a
blood sugar level on the basis of the light absorption spectrum.
For example, the blood-sugar-level calculating unit 171 calculates
a blood sugar level from the light absorption spectrum using an
analysis method such as a multiple regression analysis method, a
main component regression analysis method, a PLS regression
analysis method, or an independent component analysis method.
[0112] The storing unit 180 is realized by various IC (Integrated
Circuit) memories such as a ROM (Read Only Memory), a flash ROM,
and a RAM (Random Access Memory) or a storage medium such as a hard
disk. The storing unit 180 stores in advance or temporarily stores
every time processing is performed a computer program for causing
the blood sugar level measuring device 10 to operate and realizing
various functions included in the blood sugar level measuring
device 10, data used during execution of the computer program, and
the like. In FIG. 1, the main memory 34 and the memory for
measurement data 36 mounted on the control substrate 30 and the
memory card 22 correspond to the storing unit 180.
[0113] The storing unit 180 stores in advance a first measurement
processing program 181 for causing the processing unit 160 to
function as the light-emission control unit 161, the
light-reception control unit 162, the blood-vessel-position
acquiring unit 163, the measurement-point-candidate setting unit
164, the exercise-state determining unit 165, the blood-sugar-level
predicting unit 166, the light-amount-control-method determining
unit 168, the measurement-point selecting unit 169, the
light-absorption-spectrum generating unit 170, and the
blood-sugar-level calculating unit 171 and performing first
measurement processing (see FIG. 15), a light emitting element list
183, a light receiving element list 184, optimum distance data 185,
a light amount control method list 186, and an adjustment table
190. Further, the storing unit 180 stores, according to
implementation of measurement, blood vessel position information
200, a measurement point candidate list 210, a light emitting and
light receiving position list 220, light absorption spectrum data
230, and a measurement result DB 240.
[0114] The light amount control method list 186 stores a list of
light amount control methods selectively applied on the basis of
the predicted blood sugar level of the user 2. FIG. 11 is a diagram
showing a data configuration example of the light amount control
method list 186. As shown in FIG. 11, in the light amount control
method list 186, the number of light emitting elements D.sub.21 of
the first light amount control method applied when the predicted
blood sugar level is smaller than a predetermined threshold set as
a first range in advance and the number of light emitting elements
D.sub.23 of the second light amount control method applied with the
predicted blood sugar level is equal to or larger than a
predetermined threshold set as a second range are set. Specific
values of the numbers of light emitting elements D.sub.21 and
D.sub.23 are defined in advance according to the procedure
explained above. However, at least the number of light emitting
elements D.sub.23 is set as a number smaller than the number of
light emitting elements D.sub.21.
[0115] The adjustment table 190 includes adjustment tables 191,
193, and 195 for exercise time, for meal time, and insulin
administration time. In all the adjustment tables 191, 193, and
195, for each of adjustment conditions, adjustment amounts
corresponding to the adjustment condition are set.
[0116] FIG. 12 is a diagram showing a data configuration example of
the adjustment table for exercise time 191. As shown in FIG. 12,
the adjustment table for exercise time 191 is a data table in which
adjustment conditions and adjustment amounts are associated. In the
adjustment conditions, degrees of exercise states represented by
ranges of exercise intensity and duration of the exercise are set
stepwise. On the other hand, in the adjustment amounts, falling
widths of a blood sugar level at every measurement interval (in the
first embodiment, 1 minute) assumed according to the degrees of the
exercise states corresponding to the adjustment amounts are set.
This is because, although a blood sugar level during exercise shows
a falling tendency, a falling amount of the blood sugar level
fluctuates according to a degree of an exercise state. In the
prediction of a blood sugar level, when the exercise-state
determining unit 165 determines that the exercise state is
"exercising", the adjusting unit 167 specifies a degree of an
exercise state of the user 2 according to which adjustment
condition set in the adjustment table for exercise time 191 is
satisfied. The adjustment unit 167 adjusts the predicted blood
sugar level using an adjustment amount corresponding to the degree
of the exercise state. Consequently, it is possible to improve
prediction accuracy of a blood sugar level.
[0117] In the adjustment table for meal time 193, a plurality of
meal menus are registered as adjustment conditions. Adjustment
amounts corresponding to the respective meal menus (dietary
contents) are set. This is because, although a blood sugar level
during a meal shows a rising tendency, a rising amount of the blood
sugar level fluctuates according to a meal menu. In predicting a
blood sugar level, the adjusting unit 167 determines that a
predetermined period (e.g., 30 minutes) from the start of a meal is
meal time. When determining that it is the meal time, the adjusting
unit 167 adjusts the predicted blood sugar level with an adjustment
amount corresponding to a meal menu of the user 2 set in the
adjustment table for meal time 193. Consequently, it is possible to
improve the prediction accuracy of a blood sugar level.
[0118] In an adjustment table for insulin administration time 195,
adjustment amounts, an adjustment condition of which is
administration of insulin, is set. This is because a blood sugar
level falls after the insulin administration. In predicting a blood
sugar level, the adjusting section 167 determines that a
predetermined period (e.g., 3 minutes) from administration of
insulin is insulin administration time. When determining that it is
the insulin administration time, the adjusting unit 167 adjusts the
predicted blood sugar level with an adjustment amount set in the
adjustment table for insulin administration time 195. Consequently,
it is possible to improve the prediction accuracy of a blood sugar
level.
[0119] Note that the adjustment tables 191, 193, and 195 may be
used as tables common to all users or may be prepared for each of
the users. During exercise, during a meal, and during insulin
administration, there is an individual difference in blood sugar
level fluctuation. Therefore, if the blood sugar level fluctuation
is analyzed from a measured blood sugar level of a user in the past
and an adjustment amount is set for the user, it is possible to
further improve the prediction accuracy of a blood sugar level.
[0120] The measurement point candidate list 210 stores the light
emitting position, the light receiving position for measurement,
and the light receiving position for reference selected as a result
of the measurement point candidate setting processing. FIG. 13 is a
diagram showing a data configuration example of the measurement
point candidate list 210. As shown in FIG. 13, the measurement
point candidate list 210 is a data table in which, in association
with a measurement point candidate number, a light emitting
position 211, a light emitting position for measurement 213, a
light emitting position for reference 215 selected concerning a
measurement point candidate corresponding to the measurement point
candidate number are set. In the light emitting position 211, light
receiving element numbers of the light emitting elements 52
corresponding thereto, that is, the light emitting elements for
measurement 52-1 are registered. In the light receiving position
for measurement 213, light receiving element numbers of the light
receiving elements 54 corresponding thereto, that is, the light
receiving elements for measurement 54-1 are registered. In the
light receiving position for reference 215, light receiving element
numbers of the light receiving elements 54 corresponding thereto,
that is, the light receiving elements for reference 54-2 are
registered.
[0121] The measurement result DB 240 accumulates and stores
measurement results of blood sugar levels of the user 2 performed
to the present. FIG. 14 is a diagram showing a data configuration
example of the measurement result DB 240. In the measurement result
DB 240, measurement result data in which measurement date and time,
a measured blood sugar level, exercise intensity, meal information,
and insulin administration information are associated is generated
and added every time measurement is performed once. The meal
information is set when an operation input of the user 2 is
performed in measuring a measured blood sugar vale corresponding to
the meal information. If an operation input indicating that a meal
is started is performed, a circle mark is set and dietary content
input by operation is set. Concerning the operation input of the
dietary content, the meal menus registered in the adjustment table
for meal time 193 are displayed as a list. The operation input is
received by selection operation from the list. Similarly, the
insulin administration information is set when an operation input
of the user 2 is performed in measuring a measured blood sugar
level corresponding to the insulin administration information. If
an operation input indicating that insulin is administered is
performed, a circle mark is set.
Flow of Processing
[0122] FIG. 15 is a flowchart for explaining a processing procedure
of first measurement processing. Note that the processing explained
below can be realized by the processing unit 160 reading out the
first measurement processing program 181 from the storing unit 180
and executing the first measurement processing program 181. The
first measurement processing is started when the blood sugar level
measuring device 10 is mounted on the body of the user 2 and
predetermined measurement start operation is input.
[0123] As shown in FIG. 15, in the first measurement processing,
the processing unit 160 stays in a standby state until measurement
timing comes (NO in step a1). For example, when measurement is
performed every 1 minute, the processing unit 160 determines that
the measurement timing comes at a point when 1 minute elapses from
the last measurement timing.
[0124] When the measurement timing comes (YES in step a1), the
processing unit 160 acquires meal information (step a3) and
acquires insulin administration information (step a5). For example,
the processing unit 160 checks, every time the measurement timing
comes, whether an operation input concerning whether a meal is
started and a selection operation input for a meal menu are
performed and acquires meal information including the start of the
meal and the meal menu according to the operation inputs.
Similarly, the processing unit 160 checks, every time the
measurement timing comes, whether an operation input concerning
whether insulin is administered and acquires insulin administration
information including the administration of insulin according to
the operation input. When the operation inputs related to the meal
and the insulin administration are not performed, the processing
unit 160 determines that both the operation inputs are not
performed. The processing unit 160 generates measurement result
data concerning the measurement of this time and sets the present
time as measurement date and time. If there are the meal
information acquired in step a3 and the insulin administration
information acquired in step a5, the processing unit 160 sets the
meal information and the insulin administration information.
[0125] Subsequently, the processing unit 160 determines whether
image acquisition time comes. When determining that the image
acquisition time comes (YES in step a7), the processing shifts to
step a9. When the image acquisition time does not come (NO in step
a7), the processing shifts to step a15. For example, the image
acquisition timing may be 10 minutes or may be 1 hour. However, if
an interval of the image acquisition timing is set short, a
biological image is frequently acquired, and a blood vessel
position is acquired, measurement accuracy can be maintained. On
the other hand, as the interval is set longer, power consumption
can be further suppressed. However, for example, when a blood
vessel position under the skin does not coincide with the acquired
blood vessel position because, for example, the blood vessel moves
or when the blood vessel cannot be correctly specified, it could
occur that the measurement accuracy until the next acquisition of a
blood vessel position is deteriorated. The image acquisition timing
is set as appropriate taking into account such a situation.
[0126] In step a9, the light-emission control unit 161 causes the
light emitting elements 52 of the sensor module 50 to emit lights
all at once. The light-reception control unit 162 causes all the
light receiving elements 54 to receive (photograph) the lights and
acquires a biological image. Subsequently, the
blood-vessel-position acquiring unit 163 processes the biological
information, acquires a blood vessel position viewed from the skin
surface, and selects a blood vessel portion to be set as a
measurement target region (step a11). For example, the
blood-vessel-position acquiring unit 163 compares each of pixels of
the obtained biological image (a luminance image) with reference
luminance, performs binarization and filter processing, and
acquires a blood vessel position. Pixels having luminance lower
than the reference luminance indicate a blood vessel. The
blood-vessel-position acquiring unit 163 excludes an accuracy
deterioration factor region and selects a blood vessel portion
having length equal to or larger than the predetermined minimum
region length. The acquired blood vessel position and the position
of the selected blood vessel portion are stored in the storing unit
180 as blood vessel position information 200.
[0127] Subsequently, the measurement-point-candidate setting unit
164 performs measurement point candidate setting processing, sets a
plurality of measurement point candidates in the blood vessel
portion selected in step a11, and selects a light emitting
position, a light receiving position for measurement, and a light
receiving position for reference (step a13). In this case, the
measurement-point-candidate setting unit 164 allocates measurement
point candidate numbers to the measurement point candidates and
associates light emitting element numbers of the light emitting
elements for measurement 52-1, light receiving element numbers of
the light receiving elements for measurement 54-1, and light
receiving element numbers of the light receiving elements for
reference 54-2 to generate the measurement point candidate list
210.
[0128] In step a15, the exercise-state determining unit 165
calculates exercise intensity of the user 2 on the basis of the
detected acceleration input from the acceleration sensor 27. The
exercise-state determining unit 165 performs threshold processing
of the exercise intensity. When the exercise intensity is equal to
or larger than a predetermined threshold set in advance, the
exercise-state determining unit 165 determines that the user 2 is
"exercising". In this case, the exercise-state determining unit 165
sets the calculated exercise intensity in measurement result data
concerning the measurement of this time.
[0129] Thereafter, the blood-sugar-level predicting unit 166
performs blood sugar level prediction processing (step a11). After
the blood sugar level prediction processing is performed, the
processing shifts to step a19. FIG. 16 is a flowchart for
explaining a detailed processing procedure of the blood sugar level
prediction processing.
[0130] As shown in FIG. 16, in the blood sugar level prediction
processing, first, the blood-sugar-level predicting unit 166
predicts the present blood sugar level of the user 2 on the basis
of a transition of measured blood sugar levels in the past (step
b1). For example, the blood-sugar-level predicting unit 166 refers
to the measurement result DB 240 and reads out measured blood sugar
levels for a predetermined time in the past. The blood-sugar-level
predicting unit 166 calculates, using a publicly-known method such
as an extrapolation method, a predicted blood sugar level according
to an extrapolation straight line calculated on the basis of the
read-out blood sugar levels. The blood-sugar-level predicting unit
166 may calculate an extrapolation curved line to calculate a
predicted blood sugar level.
[0131] Subsequently, the adjusting unit 167 performs processing in
steps b3 to b7 as exercise time adjustment processing. When it is
determined in step a15 in FIG. 15 that an exercise state is
"exercising" (YES in step b3), the adjusting unit 167 refers to the
exercise intensity of the user 2 set in the measurement result DB
240 dating back to values in the past from a value of this time and
specifies a degree of the exercise state of the user 2 according to
which adjustment condition set in the adjustment table for exercise
time 191 is satisfied (step b5). The adjusting unit 167 subtracts
an adjustment amount corresponding to the specified degree of the
exercise state of the user 2 from the predicted blood sugar level
predicted in step b1 and adjusts the predicted blood sugar level
(step b7).
[0132] Subsequently, the adjusting unit 167 performs processing in
steps b9 and b11 as meal time adjustment processing. That is,
first, the adjusting unit 167 refers to the meal information of the
user set in the measurement result DB 240 dating back to values in
the past from a value of this time and determines on the basis of
most recent meal information whether a predetermined time (in the
first embodiment, 30 minutes in the past) elapses from the start of
a meal. When determining that the predetermined time does not
elapse and it is the meal time (YES in step b9), the adjusting unit
167 reads out an adjustment value corresponding to a meal menu from
the adjustment table for meal time 193 and adds the adjustment
value to the predicted blood sugar level predicted in step b1 to
adjust the predicted blood sugar level (step b11).
[0133] Subsequently, the adjusting unit 167 performs processing in
steps b13 and b15 as insulin administration time adjustment
processing. That is, first, the adjusting unit 167 refers to the
insulin administration information of the user 2 set in the
measurement result DB 240 dating back to values in the past from a
value of this time and determines on the basis of most recent
insulin administration information whether a predetermined time (in
the first embodiment, 3 minutes in the past) elapses from the
administration of insulin. When determining that the predetermined
time does not elapse and it is the insulin administration time (YES
in step b13), the adjusting unit 167 reads out an adjustment value
from the adjustment table for insulin administration time 195 and
subtracts the adjustment value from the predicted blood sugar level
predicted in step b1 to adjust the predicted blood sugar level
(step b15).
[0134] In step a19 in FIG. 15, the light-amount-control-method
determining unit 168 applies the first light amount control method
or the second light amount control method according to the light
amount control method list 186 and determines the number of light
emitting elements. Specifically, when the predicted blood sugar
level is smaller than a predetermined threshold and is low, the
light-amount-control-method determining unit 168 selects the first
light amount control method. When the predicted blood sugar level
is equal to or larger than the predetermined threshold and is high,
light-amount-control-method determining unit 168 selects the second
light amount control method. By selecting the first light amount
control method or the second light amount control method on the
basis of the predicted blood sugar level in this way, the
light-amount-control-method determining unit 168 determines the
number of light emitting elements in the case of the high predicted
blood sugar level as a number smaller than the number of light
emitting elements in the case of the low predicted blood sugar
level.
[0135] Subsequently, the measurement-point selecting unit 169
refers to the measurement point candidate list 210 and selects, as
measurement points, measurement point candidates equivalent to the
number of light emitting elements determined in step a19 (step
a21). In this case, the measurement-point selecting unit 169
allocates measurement point numbers to the selected measurement
points and associates the light emitting positions, the light
receiving positions for measurement, and the light emitting
positions for reference set in the measurement point candidate list
210 with the measurement point numbers to generate the light
emitting and light receiving position list 220.
[0136] Concerning which of the measurement point candidates are set
as the measurement points, a configuration may be adopted in which
the measurement point candidates equivalent to the number of light
emitting elements may be selected in the order of the measurement
point candidate list 210 or the measurement point candidates
equivalent to the number of light emitting elements may be selected
from the measurement point candidate list 210 at random.
Alternatively, a configuration may be adopted in which, when the
measurement point candidate list 210 is generated in step a13,
processing for rearranging the measurement point candidates in
order from the measurement point candidates, the positions of which
on the blood vessel portions are closest to the centers, is
performed in advance, and the measurement point candidates closer
to the centers are more preferentially selected than the
measurement point candidates set at the ends of the blood vessel
portions.
[0137] In the subsequent step a23, the measurement-point selecting
unit 169 performs blood sugar level measurement processing using
the light emitting and light receiving position list 220. After the
blood sugar level measurement processing is performed, the
processing shifts to step a25.
[0138] FIG. 17 is a flowchart for explaining a detailed processing
procedure of the blood sugar level measurement processing. As shown
in FIG. 17, in the blood sugar level measurement processing, the
light-emission control unit 161 causes the light emitting elements
52 for measurement to emit lights all at once to irradiate
measurement light according to the light emitting and light
receiving position list 220 (step c1). The light-reception control
unit 162 causes all the light receiving elements 54 to receive
reflected light from the user 2 (step c3). Subsequently, the
light-absorption-spectrum generating unit 170 generates a light
absorption spectrum for each of the measurement points on the basis
of light reception results in the light receiving positions for
measurement and the light receiving positions for reference
corresponding to the light receiving elements 54 (step c5) and
generates an average light absorption spectrum obtained by
averaging the generated light absorption spectra at the measurement
points (step c7). Spectrum data of the generated average light
absorption spectrum is stored in the storing unit 180 as the light
absorption spectrum data 230. The blood-sugar-level calculating
unit 171 calculates a blood sugar level from the average light
absorption spectrum generated in step c7 (step c9). In this case,
the blood-sugar-level calculating unit 171 sets the calculated
blood sugar level as a measured blood sugar level and sets the
measured blood sugar level in measurement result data concerning
the measurement of this time.
[0139] In step a25 in FIG. 15, the processing unit 160 performs
control for reading out, referring to the measurement result DB
240, a measured blood sugar level from the latest measurement
result data and displaying the measured blood sugar level of this
time on the display unit 140. Thereafter, until the measurement
ends (No in step a27), the processing unit 160 returns to step a1
and repeats the processing explained above.
[0140] As explained above, according to the first embodiment, it is
possible to calculate a predicted blood sugar level from a
transition of measured blood sugar levels measured in the past and
adjust the predicted blood sugar level taking into account exercise
intensity, meal information acquired by receiving an operation
input of the user 2, and insulin administration information.
Therefore, it is possible to accurately predict the present blood
sugar level of the user 2. When the predicted blood sugar level is
low, the number of light emitting elements caused to emit light in
measurement can be set large. When the predicted blood sugar level
is high, the number of light emitting elements caused to emit light
in measurement can be set small. Consequently, it is possible to
highly accurately perform the measurement when the predicted blood
sugar level is low and, on the other hand, reduce a light amount
per one measurement and suppress power consumption when the
predicted blood sugar level is high. Therefore, it is possible to
attain a reduction in power consumption. As a result, even in a
form of use of the blood sugar level measuring device 10 mounted on
the user 2 to repeatedly measure blood sugar levels for a long
period, for example, when a blood sugar level of a diabetic is
monitored, it is possible to use the blood sugar level measuring
device 10 for a longer period. Labors and time for charging work,
battery replacement work, and the like by the user 2 are saved.
Second Embodiment
[0141] A second embodiment can be basically realized in the same
manner as the first embodiment. However, the second embodiment is
different from the first embodiment in that a prediction error of a
predicted blood sugar level is calculated on the basis of a
measured blood sugar level obtained when the second light amount
control method explained in the first embodiment is applied and,
when the prediction error is large, the second light amount control
method is applied to measure a blood sugar level again.
Functional Configuration
[0142] FIG. 18 is a block diagram showing a main functional
configuration example of a blood sugar level measuring device 10a
in the second embodiment. As shown in FIG. 18, the blood sugar
level measuring device 10a includes the sensor unit 110, the
body-motion detecting unit 120, the operation input unit 130, the
display unit 140, the communication unit 150, a processing unit
160a, and a storing unit 180a. Note that portions same as those in
the first embodiment are denoted by the same reference numerals and
signs.
[0143] In the second embodiment, the processing unit 160a includes
the light-emission control unit 161, the light-reception control
unit 162, the blood-vessel-position acquiring unit 163, the
measurement-point-candidate setting unit 164, the exercise-state
determining unit 165, the blood-sugar-level predicting unit 166
functioning as a predicting unit, the light-amount-control-method
determining unit 168, the measurement-point selecting unit 169, the
light-absorption-spectrum generating unit 170, the
blood-sugar-level calculating unit 171, a prediction-error
calculating unit 172a functioning as an error calculating unit, and
a re-measurement control unit 173a.
[0144] The prediction-error calculating unit 172a calculates a
prediction error of a predicted blood sugar level on the basis of a
measured blood sugar level obtained when measurement of this time
is performed by applying the second light amount control
method.
[0145] When a re-measurement condition, which is a predetermined
condition indicating that the prediction error is relatively large,
is satisfied, the re-measurement control unit 173a determines the
number of light emitting elements again by applying the first light
amount control method.
[0146] The storing unit 180a stores in advance a second measurement
processing program 182a for causing the processing unit 160a to
function as the light-emission control unit 161, the
light-reception control unit 162, the blood-vessel-position
acquiring unit 163, the measurement-point-candidate setting unit
164, the exercise-state determining unit 165, the blood-sugar-level
predicting unit 166, the light-amount-control-method determining
unit 168, the measurement-point selecting unit 169, the
light-absorption-spectrum generating unit 170, the
blood-sugar-level calculating unit 171, the prediction-error
calculating unit 172a, and the re-measurement control unit 173a and
performing second measurement processing (see FIG. 19), the light
emitting element list 183, the light receiving element list 184,
the optimum distance data 185, the light amount control method list
186, and the adjustment table 190. Further, the storing unit. 180a
stores, according to implementation of measurement, the blood
vessel position information 200, the measurement point candidate
list 210, the light emitting and light receiving position list 220,
the light absorption spectrum data 230, and the measurement result
DB 240.
Flow of Processing
[0147] FIG. 19 is a flowchart for explaining a processing procedure
of the second measurement processing. Note that processing
explained below can be realized by the processing unit 160a reading
out the second measurement processing program 182a from the storing
unit 180a and executing the second measurement processing program
182a.
[0148] As shown in FIG. 19, in the second measurement processing,
after the blood sugar level measurement processing in step a23, the
prediction-error calculating unit 172a determines the light amount
control method applied in step a19. When determining that the
second light amount control method with small power consumption is
applied (YES in step d1), the predicting-error calculating unit
172a calculates an error rate of the predicted blood sugar level as
a prediction error on the basis of the measured blood sugar level
obtained as a result of step a23 and the predicted blood sugar
level obtained as a result of step a11 (step d3). When determining
that the first light amount control method is applied (NO in step
d1), the processing shifts to step a25.
[0149] Subsequently, the re-measurement control unit 173a
determines that a re-measurement condition is a condition that the
prediction error is not within a predetermined allowable error rate
set in advance (e.g., within .+-.20% considered to belong to the A
zone shown in FIG. 3). When the re-measurement condition is
satisfied (YES in step d5), the re-measurement control unit 173a
determines that the first light amount control method is applied,
reads out the number of light emitting elements of the first light
amount control method from the light amount control method list
186, and determines the number of light emitting elements again
(step d7). When the re-measurement condition is not satisfied (NO
in step d5), the processing shifts to step a25.
[0150] Thereafter, the measurement-point selecting unit 169 refers
to the measurement point candidate list 210 and selects, as
measurement points, measurement point candidates equivalent to the
number of light emitting elements determined in step d7 again (step
d9). The processing is performed in the same procedure as step a21
to generate the light emitting and light receiving position list
220 anew.
[0151] In the subsequent step d11, blood sugar level measurement
processing is performed using the light emitting and light
receiving position list 220 generated anew in step d9. The
processing is performed according to the same procedure as step a23
to rewrite the measured blood sugar level of the measurement result
data concerning the measurement of this time. Thereafter, the
processing shifts to step a25.
[0152] As explained above, according to the second embodiment, it
is possible to calculate a prediction error of a predicted blood
sugar level on the basis of a measured blood sugar level measured
by applying the second light amount control method with small power
consumption. When the prediction error is relatively large, it is
possible to measure a blood sugar level again by applying the first
light amount control method in which measurement can be relatively
highly accurately performed.
[0153] In the embodiments explained above, the light control
methods defined by the number of light emitting elements are
illustrated. On the other hand, the first light amount control
method may be defined as a light amount control method for
selecting all measurement point candidates as measurement points
rather than defining a specific number as the number of light
emitting elements. A light amount control method for selecting a
predetermined number of measurement points in order from
measurement point candidates, positions of which on the blood
vessel portions are closest to the centers from the blood vessel
portions (e.g., measurement point candidates closest to the center
in the blood vessel longitudinal direction of a certain blood
vessel portion 7b in FIG. 9) may be defined as the second light
amount control method.
[0154] In the embodiments explained above, the two kinds of light
amount control methods (the first light amount control method and
the second light amount control method) in which the number of
light emitting elements is defined in two stages of low or high of
the predicted blood sugar level are illustrated. However, the
number of light emitting elements may be determined by selectively
applying three or more kinds of light amount control methods. In
this case, value width of the predicted blood sugar level is finely
divided in three or more stages. The three or more kinds of light
amount control methods are defined to reduce the number of light
emitting elements stepwise as the predicted blood sugar level is
higher and are registered in the light amount control method list
186.
[0155] In the embodiments explained above, the light amounts
control methods are defined by the number of light emitting
elements to control a light amount per one measurement. On the
other hand, two or more kinds of light amount control methods may
be defined by an amount of electric current supplied to the light
emitting element for measurement 52-1 to control a light amount per
one measurement. For example, an amount of electric current of the
second light amount control method applied when a predicted
measurement value is high is defined smaller than an amount of
electric current of the first light amount control method applied
when the predicted measurement value is low. Alternatively, two or
more kinds of light amount control methods may be defined by an
exposure time to control a light amount per one measurement. For
example, an exposure time of the second light amount control method
applied when a predicted measurement value is high is defined
shorter than an exposure time of the first light amount control
method applied when the predicted measurement value is low. If the
amount of electric current is reduced, an S/N ratio decreases.
Therefore, although measurement accuracy is deteriorated, it is
possible to suppress power consumption. The same holds true when
the exposure time is reduced.
[0156] Alternatively, in the embodiments explained above, in order
to generate a light absorption spectrum of blood vessel transmitted
light, the light emitting element for measurement 52-1 is caused to
emit light while a light emission wavelength is shifted by
predetermined wavelength width at a time. However, two or more
kinds of light amount control methods may be defined by the
predetermined wavelength width (also considered to be a wavelength
interval) to control a light amount per one measurement. For
example, wavelength width of the second light amount control method
applied when a predicted measurement value is high is defined
longer than wavelength width of the first light amount control
method applied when the predicted measurement value is low. As an
example, the wavelength width of the first light amount control
method is set to 10 nm and the wavelength width of the second light
amount control method is set to 100 nm. When the wavelength width
(the wavelength interval) is set long, although it is possible to
suppress power consumption, measurement accuracy is deteriorated
because data of wavelength at which light is not emitted is
interpolated to generate a light absorption spectrum.
[0157] Two or more of the number of light emitting elements, the
amount of electric current, the exposure time, and the measurement
wavelength width (the measurement wavelength interval) may be used
to define two or more kinds of light amount control methods
according to a combination of the values.
[0158] In the embodiments explained above, a predicted blood sugar
level is calculated on the basis of a transition of measured blood
sugar levels in the past. On the other hand, when a measurement
interval is as short as about 1 minute as in the embodiments and
blood sugar level fluctuation from the last measurement time is
considered to be small, a measured blood sugar level obtained in
the last measurement may be predicted as a predicted blood sugar
level of this time.
[0159] In the embodiments explained above, the body-motion
detecting unit 120 is configured by the acceleration sensor 27.
Exercise intensity is calculated on the basis of detected
acceleration. On the other hand, the body-motion detecting unit 120
may be configured by an angular velocity sensor (a gyro). Exercise
intensity may be calculated on the basis of detected angular
velocity. Alternatively, the body-motion detecting unit 120 may be
configured by a pedometer. Exercise intensity may be calculated on
the basis of the number steps (a pitch) per unit time.
* * * * *